Vivaldi defeats X-Mouse functionality by jumping z-order
I use X-Mouse type functionality on windows, so I can focus a window which isn't top of the stack just by moving the mouse. But if I do this with Vivaldi, it jumps to the front as if I had clicked on it. The only other app I've come across which does this is a 12-year old copy of Lotus Notes, so I suppose it has an excuse Please don't assume because it has the focus it must be at the top of the stack... I regularly use this for cutting & pasting from other apps, and Chrome is happy to stay put, so I'm presuming it's something in Vivaldi itself...
On one of my PCs Vivaldi steals focus (forces itself to foregorund) if i want to use PuTTY (a SSH client).
Vivaldi Final has a bug which forced stealing focus from other apps, but the developers work on it as i saw internally.
I hope next Snapshot will fix it.